Curves > Merge Curve Corners connects the two ends of a single curve line, or attaches the end of one curve line to another. This function helps to refine the curve lines created with the Curves > Create / Modify Curves, and can help identify sharp edges in downstream operations.
Use Ctrl-z to undo a
Un-Named parameter group -
Connect Ends checkbox - The endpoints of curve lines will be connected to each other if they are near each other. The action will take place when you press Auto or when you simultaneously select any two endpoints (of a single line or of different lines).
Attach End to Line checkbox - The endpoints of curve lines will be connected to other nearby curve lines. The action will take place when you press Auto or when you simultaneously select an endpoint of a curve line and an intermediate point of a different curve line.
Auto button - performs the connection(s) automatically, sometimes not as accurately as a manual process. To operate manually, left-drag the cursor over the subject curve lines. Connection takes place when you release the mouse button.
OK button - saves merged curve lines to the object and closes the dialog.
Cancel button - terminates the dialog without saving merged curve lines.